Hero or traitor? Despite his conviction, the debate about how much damage was
actually done by Bradley Manning rages on.

A military court in Forte Meade made its opinion of Bradley Manning resoundingly clear last week, finding him guilty of 20 counts of espionage and related offences.

But the argument rages on about the damage done by the security breach perpetrated by the young army private, the biggest in US history.

Manning may well take the stand soon as a hearing to determine his sentence continues this week.

Facing a maximum of 136 years, the 25-year-old will claim that although he was responsible for what has been called the "9/11 of diplomacy", his actions did not lead to carnage in the real world, nor even the loss of a single life.

Those detractors argue that the former intelligence analyst yielded a weapon far mightier than his diminutive 5'2" frame could ever threaten – a set of CDs containing 700,000 mostly classified military and diplomatic documents that he passed to the website WikiLeaks, led by Julian Assange, in 2010.

PJ Crowley, the US State Department spokesman at the time, insists that local people working confidentially with the US in autocratic or difficult countries who were named in communiqués later lost their lives, though he said a causal link could not be proved.

"Julian Assange has said many times that no one got hurt by this," he told The Sunday Telegraph. "It is a fact that sources of information that were revealed in those cables were intimidated, jailed and killed. Can we say for certain they were killed because of the release of the cables? No."

Courtroom sketch of Bradley Manning, third from left, standing with lead defence attorney David Coombs, centre, Denise Lind, right, reads her verdict

Mr Crowley was not able to say how many such cases there had been, or say where they had occurred.

The question of real-world damage was raised with a prosecution witness on Wednesday, the first day of Manning's sentencing hearing, but again without hard proof. Retired Gen Robert Carr said the Taliban killed an Afghan man who had a relationship with the US.

The Taliban later said publicly the man was associated with the WikiLeaks files. The general, who led a Pentagon review of the effects of the leaks, however could not find the Afghan's name in the material disclosed by Manning.

"We went back and searched for his name in the disclosures. The name was not there," Gen Carr said. The judge later said she would disregard that part of his evidence.

Releasing so much classified material, he said, put countless people at risk. "It's a nasty world," Gen Carr said. "In some cases, lives will be harmed."

From secret assessments of detainees at Guantánamo Bay, Gen Carr said, al-Qaeda learned for the first time how individual detainees were captured, interrogated and imprisoned.

He conceded that although the mass leak "hit us in the face", the review did not find any evidence that civilians named in the secret files had then been killed or even targeted by militants.

The US war effort was however weakened, he said, because some friendly Afghan villagers feared for their lives after being named in the war logs and stopped helping US forces.

"One of our primary missions is to protect the population over there," said Gen Carr, "We had to get close to the population, had to understand that population and we had to protect them. If the adversary had more clarity as to which people in the village were collaborating with the US forces, then there is a chance that those folks could be at greater risk."

Supporters of Army Pfc. Bradley Manning flash peace signs outside a courthouse in Fort Meade after the verdict was read out

Peter King, the Republican chairman of the House subcommittee on counter-terrorism and intelligence, said the removal of cooperation alone "cost American lives" because the US war effort was rendered less effective.

A US navy officer who formerly worked at the International Security Assistance Force headquarters in Kabul told The Sunday Telegraph: "I had conversations with very high ranking intelligence officers in Afghanistan and they said it had a major impact on the way they were able to collect information and on their ability to have conversations with people who were previously forthcoming."

Asking not to be named, he reflected the dismay within the US military that Manning had violated the trust of his comrades.

"There was a lot of anger in the military towards Manning. How could somebody do something like that? If he wanted to blow the whistle, fine. But when you release 700,000 documents you're not a whistleblower, you're just an angry young man trying to be destructive."

There was undoubted fallout from the 250,000 diplomatic cables released by WikiLeaks.

Hillary Clinton, then US Secretary of State, faced calls to resign after it was revealed that she had ordered her people to filch the biometric data and computer passwords of United Nations officials, including the Secretary General.

Often in vivid language and telling detail, diplomats relayed the follies and fallibilities of foreign leaders around the world.

Gene Cretz, the US ambassador to Libya, was recalled to Washington after it became clear that Col Muammar Gaddafi was furious over a cable which suggested his relationship with his Ukrainian nurse was more than medical.

The US ambassador to Mexico, Carlos Pascual, resigned after a cable in which he criticised President Felipe Calderon was made public. Saudi Arabia made it very clear to US ambassador James Smith that they would be more reticent in talking to him following the release of cables saying that Saudi Arabia wanted the US to bomb Iran.

Mr Crowley said concern endured today that foreign sources were being less candid with American diplomats, thus eroding US influence around the world.

"What concerned us what there would be a reticence to be candid," he said. "In some cases governments made clear to us that they were going to be cautious about what they said until we could restore trust that confidentiality would be respected.

"Are governments being less candid with us? We just don't know what they're not telling us."

He also conceded that in many cases diplomatic strains caused by the leaks were "transitory" because new governments have taken over or the US has been able to smooth ruffled brows.

Steven Aftergood, an expert on government secrecy at the non-partial Federation of American Scientists, agreed. "The official damage assessments concerning Manning and WikiLeaks have not been publicly released, but my sense is that the bulk of the damage is subtle rather than catastrophic," he said.

"Nonetheless it is real. Because of the broad scope and overwhelming volume of the WikiLeaks cables, their disclosure cast doubt on the ability of the US government to guarantee confidentiality of any kind – whether in diplomacy, military operations or intelligence, that's not a small thing."

For Manning's supporters, the guilty verdicts have only deepened their admiration for his courageous stance in favour of the freedom of information and against what they see as US foreign policy hypocrisy.

From the beginning they have highlighted that revelations in the files about the Tunisian ruling family's decadence were cited by protesters who overthrew the regime of Zine al-Abidine Ben Ali at the birth of the Arab Spring. Mockery of Silvio Berlusconi contributed to him being prosecuted for having sex with an under age prostitute.

The president, he said, had initiated more espionage proceedings against whistle-blowers and publishers than all previous presidents combined.

"Throughout the proceedings there has been a conspicuous absence: the absence of any victim. The government never claimed Mr Manning was working for a foreign power. The only 'victim' was the US government's wounded pride."

Right or wrong, he will find out when sentence is passed just how wounded that pride really is.